Studies On The Effects And Mechanisms Of High Pressure Gases And Their Combined Treatments On The Shelf-life Extension Of White Mushroom (agaricus Bisporus) During Cold Storage

Health concerns have driven demand for fresh fruits and vegetables as consumers look forhealthier and more nutritious options for their diets. The ever increasing consumer demandfor high quality fresh fruits and vegetables with natural flavor and taste, free from additivesand preservatives, has triggered the the interest for the development of nonthermal innovativeapproaches for preserving and processing foods with maximum safety and quality without thedisadvantages of conventional processing. New and alternative food preservation methods, aswell as novel combinations of existing methods, are continually being sought by industry inpursuit of producing better quality foods economically. Hence, new innovations, technologies,and concepts continue to emerge.Microorganisms and enzymes are major factors in fruits and vegetables spoilage andcontrol of these factors can extend shelf life of fruits and vegetables. To meet the customer’sdemand, it is necessary to implement new preservation technologies in the food industry.Emerging nonthermal processes, such as application of pressurized inert gas, ultrasound andmodified atmosphere packaging (MAP), are such alternatives for processing foods withmaximum safety and quality.In this study, fresh white mushroom (Agaricus bisporus) was treated by some treatmentssuch as pressurized inert gas (argon and krypton), ultrasound, MAP and washing (citric acidand hydrogen peroxide). The effect of these treatments on physicochemical aspects,microbiological properties and sensory was evaluated during cold storage.Effects of ultrasound, chemical and MAP treatments on white mushroom (Agaricusbisporus) prior to high pressure gases in extension shelf-life during cold storage on theirphysicochemical and microbiological properties were studied during12days of storage at4°C. Washed samples exhibited the smallest respiration rate compared to all other samples.Hydrogen peroxide washing was effective in retaining mushrooms colour change.Furthermore, the diminishments in weight of ultrasound treated samples during storage weresignificantly (P<0.05) low in comparison with the other four treatments. The weight loss forultrasound (U) treated samples were3.52%,4.07%and4.59%for Ucitric acid, Uhydrogenperoxide and Uwater respectively. The lowest polyphenol oxidase (PPO) activity wasobserved in ultrasound treatment followed by washing treatment. Combined treatmentsshowed lower PPO activity, retained antioxidants, delayed pseudomonas growth and did notcause any decline in tissue firmness during cold storage time. Effects of high pressure argon (HA), krypton (HK) and their mixed pressure (HAK)treatments on the quality of white mushrooms were studied during9days of storage at4°C.Pressure argon at5MPa (HA5) followed by pressurised mixing argon and krypton at2.5MPaeach (HAK) treatments exhibited the smallest respiration rate, PPO activity, retained colourchange, antioxidants and delayed pseudomonas growth compared with all other samples.Respiration rate after9days of storage were5.35%,6.20%,7.50%,7.60%,7.91%and8.95%for HA5, HAK, HA2, HK5, HK2and control, respectively. DPPH inhibitionpercentage of free radical for HA5, HAK, HK5, HA2, HK2and control mushrooms were28.03%,25.24%,24.96%,21.87%,20.56%and19.06%, respectively, after9days of storage.The pressurised argon treatment was the most effective compared to pressurised krypton.Effects of ultrasound (U), high pressure argon (H) and their combination treatments (UH)on physicochemical and microbiological characteristics of white mushrooms were studiedduring9days of postharvest storage at4°C. H treated samples exhibited the smallest weightloss and respiration rate compared to all other samples. Weight losses after9days of storagewere3.01%,5.09%,5.39%and9.59%for H, UH, U and untreated mushrooms, respectively.Furthermore, U treated samples showed lower PPO activity during storage while UH treatedsamples showed a slight increase in antioxidant capacity during storage and also experiencedreduced weight loss and respiration rate. In addition, treated samples were effective inretaining mushrooms colour changes compared to untreated ones. H treatments wererelatively more effective in retaining firmness and were found to maintain the cell integrity.White mushrooms firmness after9days of storage were3.58N,3.24N,3.01N and2.79Nfor H, UH, U and untreated mushrooms respectively. Similarly, the ascorbic acid and totalsoluble solid in fresh mushroom was also greatly reduced by the H treatment. Ultrasoundtreatment followed by UH and H respectively exhibited a pronounced effect on retardingbrowning and in delaying mesophilic, psychrotophic bacteria, yeasts and moulds growth inwhite mushroom, compared to the control during9days of cold storage.The effect of high argon pressure (HAP) combined with modified atmosphere packaging(MAP) processing on the physico-chemical and microbiological characteristics of whitemushrooms were assessed during15days of storage at4°C. The comparisons betweendifferent samples showed, HAP samples exhibited the smaller rate of weight loss and higherincrease in total flavonoid and protein contents. Weight losses after15days of storage were2.3%,3.8%,4.8%and7.6%for HAP, MAP, HAP-MAP and untreated mushrooms,respectively. Furthermore, MAP treatment showed smaller PPO activity during storage. PPOactivity in white mushrooms increased during the15days of storage from initial activity of1 009U min-1g-1to2070,2418,2976and3174U min-1g-1corresponding to MAP, HAP-MAP, HAP and control treatments, respectively. MAP-HAP treatment revealed beneficialeffects on white mushroom colour, total phenol content and ascorbic acid content, andmoderate effect on total flavonoid and PPO. All treatments were effective in retardingmushroom colour change.